Re: [Qemu-devel] [PATCH] fcntl64 fix

[Stuart Anderson]

On Tue, 20 Mar 2007, Paul Brook wrote:

> > Now that the dust has settled, I see where the change is probably a
> > no-op anyway. A quick little test program indicates that on x86_64,
> > l_start will have an offset of 8 wether the structure is packed or not,
> > and wether the __pad member is present or not. The unsigned long long is
> > always going to be aligned to a 8 byte boundary.
>
> The __pad member is essential. Your logic is wrong is two ways:
>
> a) The struct is packed. This overrides normal alignment and ensures the
> structure contains no padding.

And in this case, it does remove some tail padding at the end of the
structure.

> b) long long has whatever alignment the host feels like giving it. There's no
> guarantee it's going to be 8 byte aligned.

No there isn't. This was just an observation of what occurs when
building a simple test case on x86_64.


                                 Stuart

Stuart R. Anderson                               address@hidden
Network & Software Engineering                   http://www.netsweng.com/
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